1. Field of the Invention
The present invention is broadly concerned with modified glutens and dispersions which can be used in the casting of biodegradable and/or edible gluten-based films. More particularly, the invention pertains to such glutens, gluten products, dispersions and films, and methods of fabricating the same, wherein wheat gluten is modified with a reducing agent for cleaving of disulfide bonds therein under controlled conditions which improve the rheological properties of the grain protein. Such modified wheat glutens can be used to fabricate superior films having good strength and thermal sealing properties. The dispersions of the invention can be continually cast into films using commercial film-forming equipment and without use of organic solvents.
2. Description of the Prior Art
Grain proteins, such as those derived from soy protein, or wheat or corn gluten, are commercially available and are relatively inexpensive in comparison to other biomaterials and many synthetic polymers. It has been suggested that such grain proteins and particularly the modified wheat glutens can be used to form flexible films by solution or dispersion casting, provided that the wheat glutens are used with appropriate plasticizers. Generally, it is understood that such films are insoluble in water and have good moisture permeability, but are deficient in oxygen permeability and tear strength.
In many film-forming prior procedures, the gluten-based casting solutions are prepared with alcohol and are heated to levels which substantially denature the gluten proteins and gelatinize the starch content of the solution. See, e.g., U.S. Pat. No. 3,653,925. The use of alcohol solvents renders commercial-scale processing difficult and dangerous owing to explosion hazards. Heat denaturation of the gluten proteins lowers the ultimate strength of the films and the gelatinized starch further weakens the films and creates non-transparent films.
There is accordingly a real and unsatisfied need in the art for improved techniques and products for the fabrication of wheat gluten-based biodegradable and/or edible films which yields films having better physical properties while avoiding use of large quantities of alcohol as a part of film casting solutions or dispersions.